Wiring board, and light emitting device using the wiring board

ABSTRACT

A wiring board according to one embodiment of the present disclosure includes: partitions each having insulating property; and conductive members that are respectively disposed in at least two adjacent regions among a plurality of regions partitioned by the partitions. Two of the conductive members respectively disposed in the adjacent regions are joined to each other through an opening formed on one of the partitions interposed between the two of the conductive members, to serve as part of a wiring.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/599,555, filed on May 19, 2017, which claims priority toJapanese Patent Application No. 2016-101764, filed on May 20, 2016. Thecontents of these applications are incorporated herein by reference intheir entirety.

BACKGROUND Field Of The Invention

The present disclosure relates to a wiring board, and a light emittingdevice using the wiring board.

Discussion Of The Background

For printed wiring boards (PWBs) used for LED illumination or the like,known mounting boards can be used such as an aluminum-based single-sidedboard, a CEM-3 copper clad board. For example, Japanese UnexaminedPatent Application Publication No. 2016-4770 discloses a method ofmanufacturing a light source mounting wiring board in which a wiringpattern is formed by partially removing layered copper foil by etching.

However, such a conventional PWB using copper foil is less likely tospread heat generated by a semiconductor element which consumes greatpower, such as a light emitting diode, over the copper foil. As aresult, the temperature of the semiconductor element is increased,thereby degrading the performance thereof. In manufacturing a PWB usingcopper foil, since a wiring pattern is formed by etching, resist wasteliquid, etching waste liquid or other liquid is generated during themanufacture. Further, forming the wiring pattern by wet platinggenerates plating waste liquid. Treatments of such waste liquids lead toincreased costs of conventional PWBs.

SUMMARY

A wiring board according to one embodiment of the present disclosureincludes: partitions each having insulating property; and conductivemembers that are respectively disposed in at least two adjacent regionsamong a plurality of regions partitioned by the partitions. Two of theconductive members respectively disposed in the adjacent regions arejoined to each other through an opening formed on one of the partitionsinterposed between the two of the conductive members, to serve as partof a wiring.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of a honeycomb structure as an insulatingmember according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram showing the honeycomb structure being theinsulating member, before being folded, according to the firstembodiment of the present invention;

FIG. 3 is a schematic diagram showing the honeycomb structure being theinsulating member according to the first embodiment of the presentinvention, in which conductive members and spacer members are disposed;

FIG. 4 is a schematic diagram of the honeycomb structure being theinsulating member according to the first embodiment of the presentinvention, in which the conductive members and the spacer members aredisposed and thereafter pressed, so that the conductive members and thespacer members fill the honeycomb structure without leaving empty;

FIG. 5 is a schematic diagram of a wiring board according to the firstembodiment of the present invention;

FIG. 6 is a schematic diagram of the wiring board according to the firstembodiment of the present invention, on which a protective film isformed;

FIG. 7 is a schematic diagram showing the wiring board on each of whichlight emitting elements (LEDs) are mounted, according to the firstembodiment of the present invention provided with resin frames;

FIG. 8 is a schematic diagram of a light emitting device which isobtained by cutting the wiring board on each of which the light emittingelements (LEDs) are mounted, according to the first embodiment of thepresent invention provided with the resin frames;

FIG. 9 is a schematic diagram of a wiring board according to a secondembodiment of the present invention before a protective film is formed;

FIG. 10 is a schematic diagram of the wiring board according to thesecond embodiment of the present invention on which light emittingelements (LEDs) are mounted;

FIG. 11 is a top view of the wiring board according to the secondembodiment of the present invention;

FIG. 12 is a bottom view of the wiring board according to the secondembodiment of the present invention;

FIG. 13A is a cross-sectional view taken along line A-A′ in FIG. 11;

FIG. 13B is a cross-sectional view taken along line B-B′ in FIG. 11;

FIG. 14A is a schematic diagram of a bottomed honeycomb structureaccording to an example of the present invention;

FIG. 14B is a cross-sectional view taken along line C-C′ in FIG. 14A;

FIG. 15A is a diagram showing a method of manufacturing a wiring boardaccording to a variation of the example of the present invention; and

FIG. 15B is a diagram showing the wiring board according to thevariation of the example of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, a description will be given of embodiments of thedisclosure with reference to the drawings as appropriate. A method ofmanufacturing a wiring board, a wiring board, and a light emittingdevice using the wiring board described in the following are forembodying the technical idea of the present disclosure. Unless otherwisespecified, the present disclosure is not specified to the following.Further, the description provided in one embodiment or example isapplicable to other embodiment or example. In the description of thestructure of other embodiment, identical or similar members are denotedby identical names, and their detailed descriptions are omitted asappropriate. The size or positional relationship of the members in thedrawings may be exaggerated for the sake of clarity.

In the following, a description will be given of a method ofmanufacturing a light emitting element mounting wiring board accordingto embodiments of the present disclosure with reference to the drawingsas appropriate.

First Embodiment

A method of manufacturing a wiring board according to one embodiment ofthe present disclosure includes: providing an insulating member 20 thatincludes a plurality of regions 14 partitioned by partitions 12 providedwith openings 16 at each of which adjacent ones of the regions 14 arejoined to each other; disposing conductive members 17 respectively inthe plurality of regions 14; and joining adjacent ones of the conductivemembers 17 through one of the partitions 12 to each other at the openingof the partition.

Providing Insulating Member

In the manufacturing method according to the present embodiment, theinsulating member 20 that has the plurality of regions 14 partitioned bythe partitions 12 is provided in providing an insulating member as shownin FIG. 1. The plurality of regions 14 include at least a portion whereadjacent regions 14 are connected to each other at the opening 16 of anyof the partitions 12, and at least a portion where regions 14 arepartitioned by the partitions 12 with no openings 16. The shape of oneof the regions formed by the partitions 12 as seen in a top view may behexagonal as shown in FIG. 1. Alternatively, the shape may betriangular, quadrangular, or octagonal, which can be understood from thefact that the shape of the honeycomb structure shown in FIG. 1 as seenin a top view becomes rectangular when the honeycomb structure is pulledin the longitudinal direction and each hexagonal shape becomes arectangular shape.

The wiring board is heated in a reflow oven or the like in mountingsemiconductor elements or the like. Accordingly, the insulating member20 is preferably heat-resistant. Further, the insulating member 20 isflame-retardant, having flame-retardant property of about V-0 or VTM-0in the Flammability Standard UL 94. For example, the insulating member20 may be formed out of an insulating resin film (also referred to as aninsulating resin coat or an insulating resin sheet, and for example,specifically, polyimide film, polyamide-imide film), a ceramic greensheet applicable for LTCC or the like. The partitions 12 may have athickness in the range of, for example, 10 μm to 200 μm, preferably 10μm to 100 μm.

The insulating member may be, for example, the honeycomb core disclosedin Japanese Unexamined Patent Application Publication No. 2014-87816, orthe honeycomb structure disclosed in Japanese Unexamined PatentApplication Publication No. 2007-98930. The partitions being arranged toform a honeycomb structure can achieve a reduction in weight whilereliably obtaining strength. In the case where the honeycomb coredisclosed in the Patent Publication No. 2014-87816 is used, the surfaceof the insulating member 20 may be adhesive for improvingmanufacturability of the honeycomb structure.

Each opening 16 is formed by partially removing one partition 12. Theopening 16 may be formed by removing the entire partition thatpartitions adjacent regions. Alternatively, for example as shown in FIG.1, the opening 16 may be formed by removing a portion of one partitionthat partitions adjacent regions. In order to maintain the strength ofthe insulating member, one partition 12 is preferably continuous at itsupper portion, its lower portion, or its middle portion. In FIG. 1, onepartition 12 is continuous at its lower portion in the insulating member20. Just predetermined regions are each provided with the opening attheir upper portions. It is also possible that the upper portion and thelower portion of one partition 12 are continuous and, for example, anangular (or circular) through hole is provided at the middle portion ofthe partition 12 as the opening. Alternatively, one partition 12 may becontinuous at its middle portion and provided with an opening at each ofits upper portion and its lower portion.

FIG. 2 is a diagram showing an exemplary insulating film used forforming the honeycomb structure shown in FIG. 1. The bold linesrepresent slits, the narrow lines represent mountain fold lines, and thebroken lines represent valley fold lines. As shown in FIG. 2, themountain fold lines and the valley fold lines are alternately providedon the insulating film in x direction with a predetermined cycle along ydirection which is perpendicular to x direction, and the slits areprovided at predetermined positions of the mountain fold lines and thevalley fold lines. Further, through holes 22 are provided so as to be incontact with (or so as to intersect) predetermined positions of themountain fold lines and the valley fold lines. Two mountain fold linesand two valley fold lines are alternately provided in a predeterminedcycle in parallel to x direction. The repetitive two mountain fold linesand two valley fold lines are folded at 120°, and folded back at themountain fold lines and valley fold lines being perpendicular to xdirection (i.e., folded at 180°). Thus, the honeycomb structure shown inFIG. 1 is formed. The insulating member may be formed by suitable methodother than such a film folding method. For example, the insulatingmember may be formed by joining a mountain area and a valley area of awavy insulating film to each other and layering the same (JapanesePatent Publication No. 2010-83079, Japanese Patent Publication No.2010-125637), or by extrusion molding using a mold (Japanese PatentPublication No. 2013-14134).

Disposing Conductive Members

After the providing the insulating member, as shown in FIG. 3, the atleast one conductive member 17 is each disposed in the regions 14 to bewiring paths. Further, in order to obtain a lightweight wiring board, atleast one spacer member 27 may be each disposed in the regions 14 whereconductive members 17 are not disposed.

The shape of each conductive member 17 may be spherical, prism-like,tubular, or the like. For example, in the case where a wiring board thathas through holes for mounting components having leads is manufactured,a tubular conductive member is disposed in a predetermined position. Theterm “components having leads” as used herein may refer axial componentsor radial components having leads that are inserted into the board orsockets, specifically, a bullet LED, a can package, a DIP, or the like.In the case of the conductive member 17, for example, spherical, theconductive member 17 may have a diameter in the range of 0.4 mm to 5 mm.The conductive member 17 must have good electrical conductivity and goodthermal conductivity, and specifically made of a material includingcopper, silver, aluminum, tin, gold, platinum, various kinds of solderand the like. In the case where high thermal conductivity is required,the conductive member 17 is formed of a uniform material; in the casewhere high thermal conductivity is not required, the conductive member17 may not be formed of a uniform material, and may have a layeredstructure, or may be an aggregated small particles of conductivemembers, such as a crumb structure. In the case where the conductivemember 17 has a layered structure, preferably the outer layer is made ofa material being highly electrically conductive, while the inner layeris made of a lightweight material regardless of electrical conductivity(e.g., aluminum, resin), or voids, in view of reducing weight of thewiring board. The outer surface of the conductive member 17 ispreferably smooth so that the area of the outer surface is reduced,which contributes to reducing formation of conductivity inhibitingsubstances such as oxides, and consequently contributes to establishingelectrical connection. The outer surface may be plated for discouragingformation of conductivity inhibiting substances such as oxides. Thesurface of the conductive member 17 serving as part of the upper surfaceof the wiring board is preferably highly light-reflective to lightemitted by the mounted light emitting element to improve lightextraction efficiency. Being high in solderability, the conductivemember 17 can establish good electrical connection with the lightemitting element.

The conductive member at a position where a semiconductor element thatgenerates a large amount of heat, such as a semiconductor light emittingelement, is mounted, and the surrounding conductive members arepreferably entirely formed of a member that is highly thermallyconductive. At a position where the heat dissipation property is notessential, the conductive member may be used, for example, a lightweightmember of which surface is equipped with a conductive film by plating orthe like, such as a metal-plated resin ball, for the purpose of reducingweight of the wiring board while reliably obtaining electricalconductivity.

The spacer members 27 are members that structure the wiring board, anddisposed in regions 14 excluding the regions 14 where the conductivemembers 17 used to energize wirings are disposed. Since the spacermembers 27 are not intended to be energized, the spacer members 27 maybe insulating or conductive. The spacer members 27 preferably have goodbondability with the insulating member and have predetermined mechanicalstrength, in order to ensure the mechanical strength of the wiringboard. The spacer members 27 are preferably smaller in density than theconductive members 17 (that is, being lightweight), in such a manner asto contribute toward reducing the weight of the wiring board. Forexample, the spacer members 27 may be made of thermosetting resin orthermoplastic resin. With the light emitting element mounting wiringboard, preferably the spacer members 27 near the light emitting elementmounting areas are made of a material that is less likely to absorblight from the light emitting elements nor is less likely to deterioratedue to light and heat. For example, the spacer members 27 made of aresin material preferably contain filler or the like and capable oflight blocking, and particularly are light-reflective. In the case wherethe semiconductor element (e.g., packaged LED or the like) mounted onthe wiring board is equipped with a heat sink that is not energized andprovided on the bottom surface, a spacer member 27 thermally connectedto the heat sink and/or spacer members 27 adjacent to the spacer member27 preferably has good thermal conductivity to dissipate heat from thesemiconductor element.

Joining

In joining, conductive members 17 respectively disposed in adjacentregions 14 are electrically and mechanically joined to each other at oneopening 16 provided on one partition 12 of the insulating member 20. Theconductive members 17 can be joined to each other by any appropriatejoining technique, such as compression joining, fusing, soldering, orbonding with a conductive adhesive agent. According to the joiningtechnique, joining conditions can be selected as appropriate, such aspressurizing, heating, drying and the like. For example, a conductivejoining material such as solder paste or silver paste may be disposedbetween the adjacent conductive members 17 including the opening, andthereafter the conductive members 17 and the joining member may beheated or dried so that the conductive members 17 are electricallyconnected to each other. Alternatively, each conductive member 17 may bedeformed by being pressurized by a press machine from above and/orbelow, so that the conductive members 17 are brought into contact withthe partitions 12, and so that adjacent conductive members 17 areconnected to each other through the opening 16 under pressure.Additionally, after being joined to each other under pressure, theconductive members 17 may be heated so that the conductive members 17are melted at their surfaces including nearby regions, and thereby fusedto each other. By the conductive members 17 being joined to each otherat the opening 16, as shown in FIG. 4, the conductive members 17 formpart of the wiring of the wiring board.

According to the present embodiment, for example, since the conductivemembers 17 are joined to each other through the opening 16 of theinsulating resin film, the area of the opening 16 that serves as thecurrent path can readily be greater than the cross-sectional area of theconventional PWB wiring layer. Therefore, electrical resistance of thewiring board can be lower than that of the conventional PWB wiring. Thisis explained as follows. The conventional PWB wiring employs copper foilthat has a thickness of about several tens of microns, which is a thinfilm, whereas the opening according to the present embodiment can beeasily formed to be greater than that. Further, an increase in thevolume also increases the mechanical strength of the wiring. In order toenhance the mechanical strength and the heat dissipation property of thewiring board, the respective spacer members 27 on the opposite sides ofone partition 12 may be joined to each other through the openingprovided to the partition 12.

The size of one opening 16 provided on partition 12 of the insulatingmember 20 may have, for example, a height of 1 mm, a width of 0.1 mm,and an area of 0.1 mm², or a height of 0.5 mm, a width of 2 mm, and anarea of 1 mm². The wiring resistance is inversely proportional to thecross-sectional area of the wiring and proportional to the length of thewiring. In the present embodiment, since the cross-sectional area of thewiring is the smallest at the opening 16, the cross-sectional area ofthe opening 16 influences the wiring resistance. In the presentembodiment, the area of the opening 16 can be easily increased to begreater than the cross-sectional area of the conventional PWB wiringmade of copper foil. Accordingly, the present embodiment can reducevoltage drop or power consumption due to the wiring resistance when thecurrent value is great in a circuit including a semiconductor elementwith great power consumption. An insulating resin film having athickness in the range of 12 μm to 50 μm can provide the insulatingproperty required for the partition 12. Accordingly, several tens ofmicrometers is sufficient as the thickness of the partition 12. Thesmaller thickness of the partition 12 is preferable for reducing thewiring resistance, with the partition 12 having a thickness up to about100 μm, the conductive members 17 having dimension greater than thatoccupy most length of the wiring. Accordingly, the thickness of thepartition 12 less influences the resistance value of the wiring.

Forming Metal Films

In order to improve the electrical connectivity or thelight-reflectivity of the conductive members 17, metal films 18 shown inFIG. 5 may be formed on or above predetermined areas of the surface ofthe wiring board where the semiconductor elements are mounted (i.e., theupper surface) or the back surface (i.e., the lower surface) thereof, byplating, sputtering, or adhering metal foil.

The metal films 18 may each be a single-layer film, or a multilayerfilm. Since the metal films 18 are connected to the semiconductorelements or the outside of the light emitting device via connectionterminals, connectors, or the like, the metal films are preferably madeof a material being high in electrical conductivity and thermalconductivity, and in mechanical and/or electrical connectivity.Specifically, the metal films 18 preferably contain copper, silver,aluminum, tin, gold, platinum, various kinds of solder, or the like inthe outermost film. Further, when employing light emitting elements asthe semiconductor elements, the metal films are preferably made of amaterial being high in light-reflectivity (e.g., Ag or the like). Themetal films 18 are not necessarily formed over all the conductivemembers 17. For example, the metal films 18 may be formed on or aboveany of the conductive members 17 where formation of the metal films 18is required, such as the areas for mounting the semiconductor elements,the areas for mounting the external connection terminals, or anysurrounding area of the foregoing. Forming the metal films 18 is anarbitrary step. Depending on the material or structure of the conductivemembers 17, the metal films 18 need not be formed. Further, the metalfilms 18 having high light-reflectivity may be formed not only on thesurface of the conductive members 17, but also on the surface of thespacer members 27. Thus, light from the light emitting elements isreflected also by the surface of the spacer members 27.

Forming Protective Film

As shown in FIG. 6, an insulating protective film 38 is preferablyformed by, for example, coating or adhering, on an area excludingpredetermined ones of the metal films 18 and conductive members 17,which are to be connected to external connection terminals or on whichsemiconductor elements be mounted, in the surface of the wiring boardwhere the semiconductor elements are to be mounted (i.e., the uppersurface) and/or the back surface (i.e., the lower surface) thereof, inorder to ensure an insulation distance (i.e., the creepage distance andthe spatial distance) required for the wiring board.

The protective film may be a single-layer film or a multilayer film, andmay be coating with varnish, solder resist, permanent resist, or thelike, or may be a semi-cured material such as a film or a sheet as well.In the case where the protective film is provided on the back surface ofthe wiring board, and part of the conductive members are exposed at theback surface, the protective film may be photosensitive (formed ofphotosensitive film resist). As necessary, an insulatinglight-reflective film having light-reflectivity may be used for theprotective film 38. With the light emitting element mounting wiringboard, the upper surface of the wiring board preferably has higher lightreflectivity with respect to emission light wavelength of the lightemitting elements. For example, the upper surface of the wiring board ispreferably set to exhibit a reflectivity of 70% or more of the lightemitted by the light emitting elements mounted thereon. Further,preferably the protective film 38 has higher light reflectivity than theconductive members 17 are, with respect to the light emitted by thelight emitting elements. Examples of the protective film 38 includeB-stage epoxy resin containing white-color filler, white-color varnish,or a heat-resistant resin film containing white color filler(specifically, an aramid resin film, a polyamide-imide resin film, orthe like) such as an adhesive layer-equipped white-color polyimide film.The protective film 38 also serving as an insulating light reflectivefilm can be formed on a predetermined area of the surface of the wiringboard where the semiconductor elements are mounted.

Mounting Semiconductor Elements

On the wiring board formed through the foregoing steps, for example, oneor more light emitting elements 200 are mounted as semiconductorelements. In the present embodiment, the surface-mount type lightemitting elements 200 each having a pair of positive and negativeelectrodes on its one surface are mounted on the upper surface of thewiring board as shown in FIG. 7. At this time, a pair of conductivemembers 17 or at least one metal film 18 formed thereon is/are eachelectrically connected to the positive and negative electrode of one ofthe light emitting elements 200. For the conductive connection betweenthe light emitting element mounting wiring board and the one or morelight emitting elements, solder, anisotropic conductive paste, or thelike may be used.

Examples of the light emitting elements 200 include semiconductor lightemitting elements such as light emitting diodes, laser diodes, lightemitting transistors or the like. The light emitting elements 200 may bepackaged. Alternatively, each of light emitting elements 200 may be alight emitting diode chip that has electrodes on its one surface. In thecase of light emitting diode chips, face-down mounted (junction-downmounted), or face-up mounted (junction-up mounted) may be employed.

Singulating

The wiring board 100 on which the light emitting elements 200 aremounted is cut/divided along predetermined cutting lines, therebysingulated, to provide light emitting devices 300 as shown in FIG. 8.Disposing the spacer members 27 in a greater number or disposing justthe spacer members 27 in the regions where the cutting/dividing linespass improves productivity, because blades, which are for example usedin a die for punching or in a dicer for cutting, wear slower than whenthe regions where the cutting/dividing lines pass is metal.

Further, for example, the insulating member can employ ceramic greensheet applicable for LTCC, and the spacer members 27 can employ amaterial that can be singulated by breaking, for example, glass epoxy.Therefore, the wiring board 100 may be divided and singulated bybreaking. Also a reduction in wear of the cutting/dividing tools and anincrease in the speed of cutting/dividing achieve high productivity. Asdescribed above, the method of manufacturing the wiring board accordingto the present embodiment does not employ etching nor wet plating informing the wiring pattern. Accordingly, resist waste liquid, etchingwaste liquid, and plating waste liquid are not produced in manufacture.This reduces the manufacturing costs of the wiring board.

Second Embodiment

A method of manufacturing a wiring board according to the presentembodiment includes, similarly to the first embodiment: providing aninsulating member; disposing conductive members; joining; forming metalfilms (FIG. 9); and forming at least one protective film (FIGS. 11, 12,and 13A and 13B). In the present embodiment, as shown in FIGS. 11 to13B, excluding the semiconductor elements and the external terminalconnecting portions, the surface of the wiring board is covered with aninsulating protective film 37 or a protective film 38 having lightreflectivity, and wiring function is provided by conductive membersconnected to each other at a corresponding opening not on the surfacebut the inside the wiring board.

In mounting, for example, light emitting elements as the semiconductorelements according to the present embodiment, surface-mount typepackaged light emitting diodes are mounted as the light emittingelements 200 as shown in FIG. 10. The cathode and anode on the backsurface of each surface-mount type packaged light emitting diode arerespectively electrically connected to adjacent metal films 18 (or theconductive members 17) insulated from each other by one partition 12.

The method according to the present embodiment may include cutting thewiring board. However, preferably a desired shape of the wiring board isattained in the providing insulating member, in view of reducing wasteof members.

EXAMPLE 1

As the insulating member, a honeycomb core formed of an insulating resinfilm according to the method disclosed in Japanese Patent Publication2014-87816 is provided. Specifically, the mountain fold lines and thevalley fold lines along y direction which is perpendicular to xdirection are alternately provided on an insulating transparentpolyimide film having a thickness of 36 μm as shown in FIG. 2 in itsfeeding direction (i.e., x direction) in a cycle of 3.35 mm. Slits areprovided at predetermined positions of the mountain fold lines and thevalley fold lines. Holes are provided so as to be tangent to (or so asto intersect) predetermined positions of the mountain fold lines and thevalley fold lines. Two mountain fold lines and two valley fold lines arealternately provided in a 3.2 mm cycle in parallel to x direction. Inother words, the fold lines are repeatedly provided: the mountain foldlines at a 3.2 mm interval, the mountain fold lines at a 3.2 mminterval, the valley fold lines at a 3.2 mm interval, and the valleyfold lines at a 3.2 mm interval. The repetitive two mountain fold linesand two valley fold lines are folded at 120°, and folded back at themountain fold lines and the valley fold lines being perpendicular to xdirection (folded at 180°). Thus, the honeycomb structure shown in FIG.1 is formed.

Bright tin-plated copper balls each having a diameter of 5.54 mm areinserted into a plurality of regions 14 partitioned by the partitions 12having the honeycomb structure. The plating thickness of each of thebright tin-plated copper balls is 10 μm.

The copper balls are pressurized from above and/or below, to be deformedto each become a hexagonal column. The honeycomb structure with thehexagonal columns is heated to about 235° C., so that the tin plating isfused by being melted at predetermined portions of the openings 16, andthereafter cooled. Thus, the wiring board 100 shown in FIG. 9 isobtained. The heating and fusing are preferably performed in a nitrogenatmosphere containing hydrogen by 1% to 4%, in order to improve theelectrical conductivity of the fused portions.

As shown in FIG. 11, the insulating and light-reflective protective film38 having openings at predetermined areas is formed on the upper surfaceof the wiring board 100. Further, as shown in FIG. 12, a polyimide filmhaving a thickness of 18 μm is attached on the lower surface of thewiring board 100, thereby serving as the protective film 37.

The order of forming the protective film 38 having light reflectivityand the protective film 37 may be reversed, or they may be formedsimultaneously.

In the wiring board formed in this manner, the hexagonal columnar metalpieces are fused at predetermined positions to form a wiring pattern.The insulating film is disposed around the metal pieces, so that themetal pieces are electrically insulated from each other. Applying themanner of Origami (the art of paper folding), the wiring board having aelongate shape can be fabricated.

EXAMPLE 2

As the insulating member, a honeycomb structure that has a bottomsurface and formed of an insulating resin film is provided, which isdisclosed in Japanese Patent Publication 2007-98930. Specifically,thermosetting resin coating or UV-curing resin coating is formed on aboard in which recesses are arranged in checkerboard pattern so as toleave space while avoiding burying the recesses. The center-to-centerdistance D of the recesses is 0.5 mm, and the thickness of theinsulating thermosetting resin coating is 0.154 mm.

Subsequently, the applied pressure is reduced around the board coatedwith the thermosetting resin. At the same time, the board coated withthe thermosetting resin (both the board and the resin coating) is heatedso as not to reach the thermosetting temperature in order to causeexpansion of air in the recesses, thereby deforming the honeycombmaterial of the thermosetting resin coating. The dimensions afterdeformation are as follows: a height of 0.33 mm, a recess depth of 0.25mm, a partition thickness of 0.08 mm. According to the method of thepresent example, the protective film that covers one side of the wiringboard surface is previously fabricated in the providing the insulatingmember. Thus, the manufacturing steps are simplified.

After being heated and cured (when UV-curing resin is used, irradiatedwith ultraviolet rays and cured), the board with the deformed resincoating is cooled. Then, the cured bottomed honeycomb structure isseparated from the board (FIGS. 14A and 14B).

The honeycomb partitions are partially cut (by cutting work, e.g., endmilling, or laser processing) at predetermined portions, to formopenings. The openings each have a width of 0.2 mm and a height of 0.16mm. In this manner, the insulating member is obtained which ispartitioned into a plurality of regions by the partitions havingopenings.

Solder-plated copper-clad aluminum balls (each having a diameter of 0.41mm) are respectively inserted into the regions partitioned by thepartitions of the honeycomb structure. The balls are pressurized fromabove and/or below, to be deformed to each become a hexagonal column.The honeycomb structure with the hexagonal columns is heated, so thatportions plated with solder are fused at predetermined portions, andthereafter cooled.

The protective coating film is formed on the upper surface. By themanufacturing method described above, the hexagonal columnar metalpieces are fused at predetermined positions to form a wiring pattern.The insulating resin film is disposed around the metal pieces, so thatthe metal pieces are electrically insulated from each other. Thus, thewiring board is formed.

While it has been described that the honeycomb structure with a bottomformed of an insulating resin film is the one disclosed in JapanesePatent Publication 2007-98930, the bottomed honeycomb structure may befabricated using a 3D printer (additive manufacturing, fused depositionmodeling (FDM)). Fabrication using a 3D printer can eliminate the stepof partially removing the partitions at predetermined portions andreduces waste materials, and therefore is preferable.

Further, as shown in FIG. 15A, it is also possible that metal thickfilms are formed from metal powder in predetermined shapes by lasercoating on an insulating resin film, to serve as the conductive members17. As shown in FIG. 15B, an insulating resin fills in the space (e.g.,100 μm) between the metal films, to serve as the partitions 12.

In the foregoing, the method of manufacturing a single-layersingle-sided wiring board has been described. Whereas, a plurality ofpredetermined single-layer wiring boards may be bonded to each other.For example, the single-layer single-sided wiring boards may be bondedto each other respectively being oriented in opposite directions, toserve as a double-sided wiring board. Alternatively, the single-layersingle-sided wiring boards may be bonded to each other both beingoriented in the same direction, to serve as a multilayer wiring boardincluding two or more layers.

The present disclosure is applicable to, for example, a wiring boardused for LED lighting.

According to one embodiment of the present disclosure a wiring boardincludes: partitions each having insulating property; and conductivemembers that are respectively disposed in at least two adjacent regionsamong a plurality of regions partitioned by the partitions. Two of theconductive members respectively disposed in the adjacent regions arejoined to each other through an opening formed on one of the partitionsinterposed between the two of the conductive members, to serve as partof a wiring.

This can provide a method of manufacturing a wiring board for mounting asemiconductor element that consumes great power such as a light emittingelement, while reduced costs of waste liquid treatment and the like, inmanufacture of the wiring board; a light emitting element mountingwiring board with improved heat dissipation property; and a lightemitting device using the wiring board.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A wiring board comprising: partitions each havinginsulating property; and conductive members that are respectivelydisposed in at least two adjacent regions among a plurality of regionspartitioned by the partitions, wherein two of the conductive membersrespectively disposed in the adjacent regions are joined to each otherthrough an opening formed on one of the partitions interposed betweenthe two of the conductive members, to serve as part of a wiring.
 2. Thewiring board according to claim 1, wherein the partitions that partitionthe plurality of regions form a honeycomb structure.
 3. The wiring boardaccording to claim 1, wherein at least one spacer member is disposed inat least one region where none of the conductive members are disposed,among the plurality of regions.
 4. The wiring board according to claim2, wherein at least one spacer member is disposed in at least one regionwhere none of the conductive members are disposed, among the pluralityof regions.
 5. The wiring board according to claim 3, wherein at leastone of the partitions has no opening, and wherein the at least onepartition with no opening partitions the at least one region where thespacer member is disposed.
 6. The wiring board according to claim 4,wherein at least one of the partitions has no opening, and wherein theat least one partition with no opening partitions the at least oneregion where the spacer member is disposed.
 7. The wiring boardaccording to claim 1, further comprising: at least one insulatingprotective film that covers at least one surface of the wiring boardwhile exposing at least a portion of the conductive members.
 8. Thewiring board according to claim 2, further comprising: at least oneinsulating protective film that covers at least one surface of thewiring board while exposing at least a portion of the conductivemembers.
 9. The wiring board according to claim 3, further comprising:at least one insulating protective film that covers at least one surfaceof the wiring board while exposing at least a portion of the conductivemembers.
 10. The wiring board according to claim 4, further comprising:at least one insulating protective film that covers at least one surfaceof the wiring board while exposing at least a portion of the conductivemembers.
 11. The wiring board according to claim 5, further comprising:at least one insulating protective film that covers at least one surfaceof the wiring board while exposing at least a portion of the conductivemembers.
 12. The wiring board according to claim 6, further comprising:at least one insulating protective film that covers at least one surfaceof the wiring board while exposing at least a portion of the conductivemembers.
 13. A light emitting device comprising: the wiring boardaccording to claim 1; and at least one light emitting element that ismounted on the wiring board and electrically connected to at least oneof the conductive members.
 14. A light emitting device comprising: thewiring board according to claim 2; and at least one light emittingelement that is mounted on the wiring board and electrically connectedto at least one of the conductive members.
 15. A light emitting devicecomprising: the wiring board according to claim 3; and at least onelight emitting element that is mounted on the wiring board andelectrically connected to at least one of the conductive members. 16.The wiring board according to claim 1, wherein the partitions are formedout of at least one of a polyimide film, a polyamide-imide film, or aceramic green sheet.
 17. The wiring board according to claim 2, whereinthe partitions are formed out of at least one of a polyimide film, apolyamide-imide film, or a ceramic green sheet.
 18. The wiring boardaccording to claim 1, wherein the conductive members are made of amaterial including at least one of copper, silver, aluminum, tin, gold,or platinum.
 19. The wiring board according to claim 2, wherein theconductive members are made of a material including at least one ofcopper, silver, aluminum, tin, gold, or platinum.
 20. The wiring boardaccording to claim 3, wherein the conductive members are made of amaterial including at least one of copper, silver, aluminum, tin, gold,or platinum.